1. Field of the Invention
The present invention relates to an optical module. More particularly, the present invention relates to a dual-port broadband light source that is adapted for outputting light having a broad wavelength band.
2. Description of the Related Art
In the field of optical communications, it is generally required that a light source has a broad wavelength band in order to measure optical characteristics of various elements used for the optical communication. The aforementioned is particularly true when an erbium doped fiber amplifier (EDFA) is used for an optical communication system, wherein the wavelength band of an optical signal for communication is 1520 nm to 1620 nm. Consequently, a light source is required that is capable of measuring characteristics of various optical elements in the 1520 nm to 1620 nm wavelength band. Recently, a broadband light source used with an injection locked laser diode for accommodating many subscribers at the same time, such as in a wavelength division multiplexing passive optical network (WDM-PON) has been receiving attention for possible deployment in a prospective super-high speed optical subscriber network. The conventional commercial broadband light source typically uses a white light source or an amplified spontaneous emission (ASE) of the EDFA. However, the conventional white light source has a low output. Consequently, the conventional white light source is not properly used in the case of a WDM-PON requiring a high output or used to measure the characteristics of the optical elements. On the other hand, the EDPA is not economical.
U.S. Pat. No. 6,507,429 entitled “ARTICLE COMPRISING A HIGH POWER/BROAD SPECTRUM SUPERFLUORESCENT FIBER RADIATION SOURCE”, which has been invented by and granted to Gaelle Ales et al. and incorporated by reference as background material, discloses a light source comprising: first and second optical fibers doped with rare earth elements; an optical isolator disposed between the first and second optical fibers; a first pump light source for pumping the first optical fiber; a second pump light source for pumping the second optical fiber; and a reflector for utilizing an amplified spontaneous emission output from the first optical fiber.
However, in the conventional broadband light source with the above-stated construction, the optical isolator disposed between the first and second optical fibers is created from the second optical fiber. The result is that the amplified spontaneous emission moving from the second optical fiber to the first optical fiber is intercepted. Consequently, there is a degree of energy loss, thereby reducing output efficiency to unsatisfactory levels. In addition, when the output of the first pump light source is changed to control the output of the first optical fiber, the output of the second optical fiber is also changed. Consequently, independent output control of the first and second optical fibers is difficult to achieve and efficiency suffers.